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		调用函数，不看实参数的类型不看数量
		<script type="text/javascript">
			function sum(a,b)
			{
				console.log(a+b);
			}
			sum("hello","lrt");
			sum(5);  //5+undefined
			sum(5,25,30);
			
			function sum1(a,b,c)
			{
				var d=a+b+c;
				return d;   //后面不跟值相当于undefined
			}
			console.log("5+25+30="+sum1(5,25,30));
		</script>
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